This Core collects long-term follow-up data for patients who have had hematopoietic cell transplantation (HCT) at the Seattle Cancer Care Alliance, University of Washington Medical Center or Children's Hospital and Regional Medical Center under protocols developed at the Fred Hutchinson Cancer Research Center as part of clinical research studies sponsored by this program. With this focus in mind, the services of this core unit address several closely related areas: identification and management of late complications, data collection, database assembly and evaluation of the efficiency, accuracy, quality and utility of the data collection and the system in which the data are stored. Chronic graftversus- host disease and late infections are prominent among the complications to be followed with support from this core unit. A variety of mechanisms have been developed to support this overall goal. a) This Core will continue to collect long-term data focused on survival, therapy-related complications, health and health-related quality of life relevant to the clinical research studies sponsored by this grant. This includes the retrospective cohort of patients currently in follow-up from previous studies and the prospective cohort of patients to be enrolled in studies. For this purpose, a system has been established to track and maintain contact with patients and referring physicians so that data can be collected at specified time points after treatment. b) This Core will continue to assist investigators in obtaining information that is not routinely collected when needed for individual research projects. c) This Core will continue to identify barriers that interfere with long-term follow-up and develop methods that could improve participation. d) This Core will continue to evaluate the research methods employed in data collection and database management, including the efficiency, reliability, validity and utility of the instruments used in the LTFU core. The data generated from this core unit will assist project leaders in the identification of late complications after HCT and help in the development of methods for improved management or prevention of these complications. The data could help to generate hypothesis-driven research concerning risk factors for late complications, the pathophysiology leading to late complications, and the development of methods for preventing late complications after HCT.